The first land-walking vertebrates may have emerged from salty estuaries

An analysis casts doubt on views that the ancient creatures arose in freshwater

tetrapod illustration

SALTY SCENE  The planet’s earliest four-footed vertebrates called tetrapods (illustrated) lived in the brackish waters of an estuary or delta, new research suggests.

Mazan

Earth’s earliest land-walking vertebrates didn’t paddle about in freshwater lakes or rivers. Instead, these four-footed creatures, which appeared about 375 million years ago, lived in the brackish waters of an estuary or delta, researchers report online May 30 in Nature.